Pollinators
of fig trees

Consideration
of how fig trees are pollinated may leave the observer with a conundrum.
Pollinators of plants can often be predicted, based on flower
characteristics of colour, fragrance and shape. For example, white,
fragrant flowers with a long corolla tube are usually pollinated by Hawk
moths, which are nocturnal and have a long tongue. Fig trees are unique in
that the flowers are completely concealed within the fig, an enclosed
inflorescence, with the hundreds of tiny florets lining the inside of a
central cavity. Attempting to guess who pollinates figs and how the act is
carried out would no doubt lead to the conclusion that the pollinator, as
for many plant species, must be highly specialized. Careful, close and
patient observation of figs that are receptive for pollination would
enlighten the observer to a fascinating world, for fig trees are
completely dependant on tiny wasps, a couple of millimeters long, for
their propagation and survival. These fig wasps are the sole pollinators
of fig trees and in turn, fig wasps can breed nowhere else but inside
figs, a relationship that is a classic example of an obligate mutualism
(neither party can survive without the other) that has evolved over the
last 60 or so million years.

Fig wasps emerging from the fig of Ficus
sur they have bred in.

Ceratosolen capensis the
pollinator of Ficus sur on a finger to illustrate the small
size of fig wasps.

Ceratosolen capensis emerging
from her gall inside a fig of Ficus sur.

Each
fig tree species is usually pollinated by one fig wasp species that is
only associated with that fig species, a host-specific relationship that
plays a major role in the prevention of hybridisation between different
species of fig trees. However, only 300 of a potential 750 fig wasp
pollinator species are currently known (there are 750 species of Ficus
in the world), and already we know that the one-to-one rule between fig
tree and wasp does not always hold, so the interaction is not as well
defined as initially appears. What the exceptions do tell us, however, is
that we are dealing with a continually evolving dynamic system, the
intricacies of which we are only just beginning to understand.